TIL Therapy

Hi
My mother has been recently diagnosed with secondary breast cancer. I have been looking for treatment options in case, if at all her current hormone therapy fails. I came across this TIL Therapy, which has given some durable response. However, I haven’t seen many persons who have exhausted all treatment options having enrolled in the trial. Is there a reason to this? Does anyone know why this treatment not being more widely used/ taken part in/ sped up despite these results? 

I don’t think we’re really aware of it in the UK and not sure there are trials here for breast cancer.  More info at this link from the US for others. nih.gov/news-events/news-releases/nih-study-advances-personalized-immunotherapy-metastatic-breast-cancer